The invention relates in general to the field of optical assemblies, optical devices, and, more generally, to solutions to connect an optical guiding element to the lid or encapsulation of an optical package.
Many optical coupling solutions are known. For example, US20120177381 (A1) discloses a solution relying on direct fiber interface or attaches to chip using optical coupling elements, which contain fibers or deflecting elements (e.g., mirrors, lenses) assembled onto a photonics die. An out-of-plane optical coupling is obtained, due to grating couplers on the photonics die.
In general, optical off-package connections are difficult because of the dimensions of the components and the force loads involved. For example, characteristic lengths of the components on die or within the package are typically less than 100 μm, while characteristic lengths outside the die/package are usually larger than 250 μm, which typically results in total lengths larger than 20 mm.
Using stiff parts to bridge the dimension gap bears the risk to introduce large levering forces into sensitive package parts, such as solder interconnects. If fiber tails extend over the package dimensions they bear the same risk. In addition, packaging processes are usually limited to some maximum sizes and cannot be implemented with a fiber tail footprint.
Using flexible parts to bridge the dimension gap poses other problems as such parts cannot be aligned to the inner part of the package after encapsulation. Indeed, after encapsulation, at least some of the parts are not accessible anymore and therefore their relative positions cannot be adjusted. Finally, encapsulation and lidding processes often require (high) temperatures that are incompatible with the optical components.